Sala A, Voelkel N, Maclouf J, Murphy R C
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver 80206.
J Biol Chem. 1990 Dec 15;265(35):21771-8.
Radiolabeled leukotriene (LT) E4 was infused into three healthy subjects in order to assess the production and elimination of sulfidopeptide leukotriene metabolites in urine. Three different radiolabeled tracers were employed, [14,15-3H]LTE4, [35S]LTE4, and [14C] LTE4 in five separate infusion studies. There was a rapid disappearance of radioactivity from the vascular compartment in an apparent two-phase process. The first elimination phase had an apparent half-life of approximately 7 min. Radioactivity quickly appeared in the urine with 10-16% eliminated during the first 2 h following intravenous infusion; 7%, 2-5 h; 4%, 5-8 h; 4%, 8-15 h; and 1.5%, 15-24 h from the [14C] LTE4 experiments. Unmetabolized LTE4 was the major radioactive component in the first urine collection, but at later times two more polar compounds predominated. After extensive purification by normal phase-solid phase extraction and reverse-phase high performance liquid chromatography, these compounds were characterized by UV spectroscopy, co-elution with synthetic standards, negative ion electron capture gas chromatography/mass spectrometry, and tandem mass spectrometry. The two major urinary metabolites were structurally determined to be 14-carboxy-hexanor-LTE3 and the conjugated tetraene, 16-carboxy-delta 13-tetranor-LTE4. Three other minor metabolites were detectable in the first urine collection only and were characterized by co-elution with synthetic standards as 16-carboxy-tetranor-LTE3, 18-carboxy-dinor-LTE4, and 20-carboxy-LTE4. omega-Oxidation and subsequent beta-oxidation from the methyl terminus appeared to be the major metabolic fate for sulfidopeptide leukotrienes in man. The accumulation of the 14-COOH-LTE3 and 16-COOH-delta 13-LTE4 may reflect a rate-limiting step in further oxidation of these compounds which places a conjugated triene or conjugated tetraene, respectively, two carbons removed from the CoA ester moiety. Also in the first urine collection there was another minor metabolite identified as N-acetyl-LTE4, however, no subsequent beta-oxidation of this metabolite was observed. The major metabolites of LTE4 might be useful in assessing in vivo production of sulfidopeptide leukotrienes in humans.
为评估尿中硫肽白三烯代谢产物的生成与消除情况，将放射性标记的白三烯（LT）E4注入三名健康受试者体内。在五项独立的输注研究中，使用了三种不同的放射性标记示踪剂，即[14,15 - 3H]LTE4、[35S]LTE4和[14C]LTE4。放射性在血管腔室中呈现出明显的双相过程快速消失。第一个消除相的表观半衰期约为7分钟。放射性迅速出现在尿液中，静脉输注后的前2小时内消除了10 - 16%；2 - 5小时为7%；5 - 8小时为4%；8 - 15小时为4%；15 - 24小时为1.5%（来自[14C]LTE4实验）。未代谢的LTE4是首次尿液收集时的主要放射性成分，但在随后的时间里，另外两种极性更强的化合物占主导地位。通过正相 - 固相萃取和反相高效液相色谱进行广泛纯化后，这些化合物通过紫外光谱、与合成标准品共洗脱、负离子电子捕获气相色谱/质谱和串联质谱进行表征。两种主要的尿代谢产物在结构上被确定为14 - 羧基 - 己基 - LTE3和共轭四烯16 - 羧基 - δ13 - 四氢 - LTE4。另外三种次要代谢产物仅在首次尿液收集时可检测到，通过与合成标准品共洗脱被表征为16 - 羧基 - 四氢 - LTE3、18 - 羧基 - 二氢 - LTE4和20 - 羧基 - LTE4。从甲基末端开始的ω - 氧化和随后的β - 氧化似乎是人体内硫肽白三烯的主要代谢途径。14 - COOH - LTE3和16 - COOH - δ13 - LTE4的积累可能反映了这些化合物进一步氧化过程中的限速步骤，这分别使共轭三烯或共轭四烯从辅酶A酯部分去除两个碳原子。同样在首次尿液收集时，还有另一种次要代谢产物被鉴定为N - 乙酰 - LTE4，然而，未观察到该代谢产物随后的β - 氧化。LTE4的主要代谢产物可能有助于评估人体内硫肽白三烯的体内生成情况。
